New ternary phase of Bi3Se2Te thin films were successfully grown through pulsed laser deposition with a single Bi2Se2Te crystal as the target. Bi-rich and Se- and Te-deficient compositions deposited at a substrate temperature (Ts) of 250°C and helium gas pressures (PHe) ranging from 2.0 × 10-5 to 6.5 × 10-1 Torr aided the formation of the dominant Bi-rich phase: Bi3Se2Te. The films were grown epitaxially on Al2O3 (001) substrates with Bi3Se2Te //Al2O3  and Bi3Se2Te //Al2O3 . An increase in PHe remarkably enhanced the hardness and Young's modulus of the films, primarily because of the decrease in nanograin size, following the Hall-Petch relationship. Moreover, the Bi3Se2Te films present linear magnetoresistance under a high perpendicular magnetic field (B ≥ 4 T) and two-dimensional weak antilocalization effect under a low B (±1 T) which may be attributed to topological insulator surface state (TSS). Clearly, further theoretical calculations and experiments are needed to confirm the suggested interpretation.